This invention relates to a method of preparing fine metal powder with a narrow particle size distribution. This invention further relates to a method of preparing amorphous and microcrystalline metals.
Metal powders are prepared commercially using chemical, electrolytic, mechanical comminution, plasma melting and atomization methods. In all processes, control over powder chemistry, cleanliness, size and shape is important.
Elemental and prealloyed metals powders are typically prepared by atomization processes. In water atomization, disintegration of the molten metal stream is brought about by impact from a high pressure stream of water. Large quantities of energy are used and the efficiency of the process of preparing particles with controlled narrow distribution is low. In general, water-atomized particles are irregularly shaped with rough oxidized surfaces.
The principle of gas-atomization is similar to that of water-atomization. A continuous stream of molten metal is broken down into droplets by a subsonic or supersonic gas stream. The particles are normally spherical and relatively smooth. However, like the water-atomization process, the process has low overall efficiency. The particle sizes obtained from these processes depends on random factors.
Reducing the number of processing steps necessary to obtain fine metal powders of narrow particle size distribution is desirable from a reduced costs and improved processing conditions standpoint.